Effect of clonidine on beta-endorphin, ACTH and cortisol secretion in essential hypertension and obesity

The role of alpha 2-adrenoceptor stimulation by clonidine on the secretion of beta-endorphin, ACTH, and cortisol in essential hypertension and obesity was studied in 45 subjects: 15 non-obese hypertensives, 10 obese hypertensives, 11 obese normotensives, and 9 healthy subjects. The circadian rhythm of plasma beta-endorphin, ACTH, and cortisol was determined after placebo and after three days on clonidine 0.45 mg daily. Clonidine lowered the blood pressure and blood ACTH and cortisol levels in all the subjects. A significant decrease in beta-endorphin after clonidine occurred in the healthy subjects. In obese normotensives basal beta-endorphin concentrations were significantly higher than in healthy subjects and did not change after clonidine. In about 50% of non-obese and obese hypertensives a significant increase in beta-endorphin secretion after clonidine was noted (responders). In the subgroup of non-obese hypertensive responders no circadian rhythm of beta-endorphin was observed. The results suggest that adrenergic regulation of beta-endorphin secretion is altered in obesity and in certain patients with essential hypertension.